Here's a breakdown:

* Wave: A disturbance that travels through a medium or space, transferring energy without transferring matter.

* Wavelength: The distance between two identical points on successive waves, such as the distance between two crests or two troughs.

Think of it like this: Imagine a rope tied to a pole, and you shake the rope up and down. The distance between the highest points (crests) of two consecutive waves is the wavelength.